Re: [PATCH 4/9] srcu: Validate callback arguments

[Paul E. McKenney]

On Fri, Oct 23, 2026 at 06:18:36PM +0800, Kunwu Chan wrote:
> Check callback-head alignment and reject NULL callback
> functions in the SRCU callback registration paths.
> 
> Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>

For 4/9-6/9:

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

> ---
>  kernel/rcu/srcutiny.c | 7 +++++++
>  kernel/rcu/srcutree.c | 7 +++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
> index 3ee28885b96f..98864977bed2 100644
> --- a/kernel/rcu/srcutiny.c
> +++ b/kernel/rcu/srcutiny.c
> @@ -291,6 +291,13 @@ EXPORT_SYMBOL_GPL(srcu_defer_drain);
>  void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
>  	       rcu_callback_t func)
>  {
> +	/* Misaligned rcu_head! */
> +	WARN_ON_ONCE((unsigned long)rhp & (sizeof(void *) - 1));
> +
> +	/* Avoid NULL dereference if callback is NULL. */
> +	if (WARN_ON_ONCE(!func))
> +		return;
> +
>  	/* Record the caller: the irq_work's stack says nothing about it. */
>  	kasan_record_aux_stack(rhp);
>  
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index 46fe2f0cef85..1993ddbdb828 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -1529,6 +1529,13 @@ static void srcu_do_enqueue(struct srcu_struct *ssp, struct rcu_head *rhp,
>  static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
>  			rcu_callback_t func, bool do_norm)
>  {
> +	/* Misaligned rcu_head! */
> +	WARN_ON_ONCE((unsigned long)rhp & (sizeof(void *) - 1));
> +
> +	/* Avoid NULL dereference if callback is NULL. */
> +	if (WARN_ON_ONCE(!func))
> +		return;
> +
>  	if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC))
>  		return; // Leak the callback rather than corrupt SRCU state.
>  
> -- 
> 2.43.0
>